SimpanKira does not have specific function to perform contra on the sales invoice or purchase invoice.
However, there is a way on how to do that on our cloud accounting software.
First, you must enable the Payment option at the Suspense account in your Liability type account. This Suspense account is default account set in your Chart of Account.
Then follow these steps;
At Sales Invoice
1) Find the Sales Invoice for the Contact that you want to contra his Purchase Invoice
2) Record payment you want to contra at the Sales Invoice.
3) Make sure you select the Suspense account in Paid To section at Receive a Payment area.
4) Put relevant information at Reference to remind you about the contra.
At Purchase Invoice
1) Find the Purchase Invoice for the Contact that you want to contra his Sales Invoice
2) record payment you want to contra at the Purchase Invoice.
3) Make sure you select the Suspense account in Paid From section at Make a Payment area.
4) Put relevant information at Reference to remind you about the contra.
Refer to the video below if you need further clarification.